1. Field of the Invention
The present invention relates to a tape reel drive system for a video recorder/reproducer and, more particularly, to a tape reel drive system for positively engaging a pair of tape reels and simultaneously taking up any slack in the tape extending between the reels.
2. Description of the Prior Art
Video recording tape is commonly supplied in a standard type cassette to eliminate the problems associated with open reels and the threading of the tape into a video recorder/reproducer. A variety of video recorder/reproducers have been developed for receiving standard video cassettes.
When using a standard video cassette with a video recorder/reproducer, the first problem becomes that of mating and demating the reels within the cassette to the reel drive system of the recorder/reproducer. For this purpose, a number of different systems have been developed for receiving the video cassette and lowering it onto a pair of reel drive hubs which receive the reels for driving the tape in opposite directions.
The cassette loaders and tape reel drive systems that have been developed heretofore have been intended for use with video recorder/reproducers designed for recording and playing back standard television type signals. In such systems, the tape travels at relatively low speeds, typically 33/4 inches per second during play back and 45 inches per second during rewind. The drive hubs typically have one or more pins which engage corresponding holes in the reels for driving of the reels by the hubs. The reels simply sit on the hubs, with no positive gripping force other than that provided by gravity.
On the other hand, the present tape reel drive system is intended for use with a video recorder/reproducer designed for use in a document acquisition and retrieval system. This environment places a number of constraints on the video tape, the cassette, and the reel drive system which cannot be accommodated with conventional loaders and reel drive systems. For example, the present reel drive system is intended for use in a system where tape travels in two directions, during a search mode, at speeds in excess of 400 inches per second. It is obvious that when tape is run at such speeds, there must be a positive connection between the drive hubs and the tape reels. Still further, when used in a document acquisition and retrieval system, it is desirable that the recorder/reproducer be positionable at any angle, not necessarily horizontal, so that gravity cannot be relied upon to insure contact between the reel drive hubs and the tape reels.
Once a video cassette is loaded into a video recorder/reproducer, an mechanism is typically employed to withdraw the tape from the cassette so that it may be engaged with the video recording and reproducing heads. To prevent jamming of the tape during this withdrawal process, it is important that the tape reels be rotated to eliminate slack in the tape therebetween. If there is any significant amount of slack in the tape between the reels, the tape withdrawal mechanism may not operate properly. Heretofore, it has been necessary to twist the tape reels by hand before loading a cassette into a system in order to take up the slack. However, since operators typically forget to perform this operation, numerous occasions of tape jamming result.